Reduced-Intensity Conditioning with Busulfan and Fludarabine for Allogeneic Hematopoietic Stem Cell Transplantation in Acute Lymphoblastic Leukemia.

Objective: Allogeneic hematopoietic stem cell transplantation (HSCT) with optimal conditioning has helped better long-term survival in acute lymphoblastic leukemia (ALL). This study investigated the efficacy and safety of reduced-intensity conditioning (RIC) with busulfan and fludarabine in adult ALL patients unfit for myeloablation.

Methods: Records of 78 patients who underwent HSCT with RIC consisting of 3.2 mg/kg/day of busulfan for 2 or 3 days and 30 mg/m²/day of fludarabine for 5 or 6 days were analyzed.

Results: The median age at diagnosis was 49 years. Over a median follow-up of 22 months, 2-year estimates of relapse-free survival (RFS) and overall survival were 57.4% and 68.7%, respectively. Multivariate analysis showed a trend of improved RFS in patients with chronic graft-versus-host disease (GVHD) (hazard ratio, 0.53; 95% confidence interval, 0.26-1.08; p=0.080). The cumulative incidences of relapse and non-relapse mortality were 42.9% and 19.6%, respectively and one case of central nervous system relapse was noted. No hepatic veno-occlusive disease was reported. Grade II-IV acute GVHD and any grade chronic GVHD occurred in 21.1% and 41.7%, respectively.

Conclusions: RIC with busulfan and fludarabine is an effective and safe conditioning regimen for adult ALL patients unfit for myeloablation.